Step 1Trim any excess fat from the lamb. Cut the chops into 1 1/2 -inch chunks with the bones.
Step 2Soak the raisins in warm water for 15 minutes to rehydrate them.
Step 3Meanwhile, place the lamb, grated onion, Moroccan spice mixture, cubeb berries or cayenne, saffron, cinnamon stick, 1 teaspoon salt, butter and half the oil in the tagine. Place on a heat diffuser if possible, uncovered, over low heat until the aroma of the spices is released, about 10 minutes. Do not brown the meat. Add the half-cup hot water and gently increase the heat to slowly bring it to a boil.
Step 4Drain the raisins. Cover the meat mixture with the onion slices and raisins and spread the tomatoes, cut side down, on top. Cover the tagine, reduce the heat to low and cook until the lamb is tender, about 2 hours.
Step 5When the lamb is almost ready, set an oven rack on the middle shelf of the oven. Heat the oven to 350 degrees.
Step 6Remove the top of the tagine and tilt the pot to pour all the liquid into a medium conventional skillet. Skim the fat off the top of the liquid; then boil it down to three-fourths cup. Season with salt and pepper to taste. Spread the reduced juices over the tomatoes in the tagine. Remove and discard the cinnamon stick. Scatter the sugar and ground cinnamon on top. Place in the oven and bake, uncovered, for 45 minutes. Switch the oven heat to broil, dribble over the remaining oil, and cook until crusty and lightly charred, about 5 minutes. Serve at once or reheat gently over medium heat.
Step 7Just before serving, warm the tortillas, tear them into large pieces, and spread about one-third over a large serving platter. Spoon about half the contents of the tagine on top. Repeat with another third of the tortillas and the remaining contents of the tagine. Top with the last of the tortillas and a sprinkling of parsley and serve at once.